Code game



Nov. 29, 1966 J, w. RYAN ETAL 3,287,825

CODE GAME Filed Feb. 18, 1965 5 Sheets-Sheet l w Q Q N f s, C

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CODE GAME Filed Feb, 1,8y 1955 ma 5 Sheets-Sheet g 7p /j//a l l l .60 ll l w ,1' 3 Il Y i v l l l f @40 7 ll l, I l l l k l Zo Il, l f l I Z0 l l N z l 0 409'@ ,fd fw() ff aaa 5M 7900 Va/2.51@ 7W 4,1/6 Speam 5 I NVENTORS JAW M /P//w By/y/P/f {ZW/g .1.W. RYAN ETAL Nov. 29, w66

CODE GAME 3 Sheets-Sheet 3 Filed Feb. 18, 1965 ww bv mk ma Q United tates Patent O CUDIE GAME lohn W. Ryan, 688 Nimes Road, Bel Air, Calif., and Conrad B. Sloop, 1518 Magnolia, Long Beach, Calif. Filed Feb. 18, 1965, Ser. No. 433,694 16 Claims. (Cl. 35-2) This invention relates generally to the coding and decoding of messages, and particularly to game apparatus for producing and deciphering hidden writings, which are either verbal or graphic, by the use of two or more different inks or other coloring media with similar appearance.

Children, and at least some adults, enjoy the creation of secrets and magic such as secret pass words, codes, and disappearing objects. They particularly enjoy the mystification or amazement of their playmates, and their own feeling of superiority, if they can create and control something which their playmates cannot understand or use.

The employment of secret codes, hidden writings, and simulations of the efforts of spies and counterspies are attractive to children. The object of such endeavors generally is to produce something which appears innocuous or unintelligible, but which contains some hidden meaning which the initiate can discover. Verbal messages are written in invisible ink which, upon heating or other treatment, is made visible on a writing surface which previously was blank or bore a different message. Complicated line drawings of an innocuous scene have been devised which, when patiently examined from different angles, contain one or more smaller drawings of different or unrelated figures or scenes. Verbal messages are encoded or garbled by children using pig latin, transposing the terminal sounds of words to the initial sounds and adding an arbitrary terminal sound to each word. Many more elaborate codes, such as arbitrary and systematic transposition and substitution ciphers, are well known.

Games are also known in which the player is required to view the game apparatus through colored transparencies. Some objects or symbols in the game are of a corresponding color; hence the players cannot see them so long as they view the game only through the color transparencies, and some surprise or training value is achieved by their efforts to play the game while viewing it through the transparencies.

Utilization of many of the prior games and devices, and the entertainment value associated with their employment, have tended to suffer either because the discovery of the hidden material was equally easy for all people who knew of the game or device (or indeed was inevitable for anyone who was not artifically prevented from discovering it) or because they required relatively elaborate equipment or procedures which were particularly less appropriate for younger children.

It is a primary object of the present invention, in view of the foregoing, to provide simple, reliable and inexpensive means for encoding and decoding messages, including both verbal messages and graphic messages such as pictures, maps and the like.

It is a further object of the present invention to provide a game, particularly for children, enabling the players to encode and decode verbal messages without the use of any ability other than the ability to spell, and to encode and decode graphic messages without even the ability to spell.

Yet another object of the invention is to provide game apparatus for producing coded messages which can be decoded immediately without any alteration or treatment of the message materials.

ICC

A still further object of this invention is to provide a coding game in which encoding and decoding can be accomplished efficiently only by use of the game apparatus.

Another object of this invention is to provide realistic simulated espionage equipment.

Other objects and advantages of the present invention will appear from the following description and drawings, which describe a preferred exemplary embodiment of the present invention as well as alternative embodiments.

In general, the present invention concerns a game in which letters or other symbols are written in two 0r more inks or other marking media which appear indistinguishable to the naked eye, but which are separated and thereby distinguished when viewed through an optical lter. Thus a message may be encoded by writing or drawing it with a first such marking means and interspersing in the message other confusing or deceptive symbols or markings with the second such marking means.

For example, a message may be Written in a black medium having no substantial intensity within the visible spectrum, and then garbled by the addition of markings in a second indistinguishable near-black medium having substantial intensity at wavelengths near the end of the visible spectrum. When this is viewed through an optical filter which transmits the visible wavelengths at which the second medium has substantial intensity but which does not transmit substantial intensities in most of the remainder of the visible spectrum, the entire surface upon which the message was written appears to be much the same color as the second medium. The confusing markings in the second medium are therefore noticeably faint or invisible, while the black markings of the first medium still stand out in distinct contrast to the surface on which they were written.

In any case, since the two marking media are indistinguishable to the naked human eye the coded message is completely visible and yet meaningless or deceptive to the ordinary Viewer without the filter. However, it can be decoded immediately by viewing it through the filter means which block out or otherwise distinguish the confusing or deceptive markings, leaving the original message clear and comprehensible.

In the drawings:

FIGURE 1 is a graphic representation of the relative sensitivity of the human eye at different wavelengths of light;

FIGURE 2 is a graphic and schematic representation of the spectra of two coloring media, and of the transmission characteristics of an optical filter, of the present invention;

FIGURE 3 is a highly schematic representation of the spectra of two coloring media, and of ,the transmission characteristics of an optical filter, of this invention;

FIGURE 4 is a perspective view of a toy pen with which the invention may be utilized;

FIGURE 5 is a sectional View taken along lines 5-5 of FIGURE 4; and

FIGURE 6 is a fragmentary perspective view of a modified form of toy pen with which the invention may be employed.

The spectrum of wavelengths to which the ordinary human eye is effectively sensitive ranges from about 4000 angstroms to about 7000 angstroms. The ability of the naked eye to distinguish between different wavelengths varies from individual to individual, as in the case of people with partial color-blindness, and varies from one area of the visible spectrum to another. FIGURE l illustrates, graphically and schematically, the relative sensitivity of the human eye. Arbitrarily assigning a value of 1.0 to lthe maximum sensitivity at about 5200 angstroms, the ordinates of the graph 2 indicate the relarl) tive sensitivity of the eye to a given level of energy at the wavelength defined by the corresponding abscissa. It will be noted that the eye is relatively quite sensitive in the middle region of the spectrum and quite insensitive in the region toward the ends of the spectrum at about 4000 and 7000 angstroms.

However, optical filter means such as those, for example, commonly used with photographic equipment, may be much more sensitive .to wavelength differences than the unaided eye and can separate colors which are substantially or wholly indistinguishable to the naked eye.

FIGURE 2 is a graph which illustrates schematically the spectra of Itwo marking media, for example inks, which each produce a black or nearly black impression when viewed by the naked eye. The spectrum of the first ink is indicated by heavy line 4 and the spectrum of the second ink by fine line 6. The ordinate for each ink indicates the relative intensity of light it produces at the wavelength defined by the corresponding abscissa.

To avoid extended exegesis upon the physical nature of colors and the sensations produced by them, lthe invention will be described in terms of .the use of marking media upon a white surface viewed in a white light, which are the normal conditions in which the invention would be used. Those skilled in the art will understand, upon the basis of the following description, that the invention may be employed with colored surfaces so long as the surfaces produce substantial intensities over a wide enough range of visible wavelengths so that a distinct contrast between both media and the surface is provided in unaided viewing, and a distinct contrast between one medium and the surface is pr-ovided when viewed through the filter means. Similarly, the invention may be employed with light sources which do not include substantial intensities at all visible wavelengths but do include substantial intensities at the principal visible wavelengths of at least one of the marking media and at enough of the remainder of the visible spectrum to provide contrast vwith'the background surface. The invention is applicable to both reflective media and background surfaces and to transparent media and background surfaces, but is best understood in terms of essentially reflective media such as pencils or inks used on ordinary paper or opaque game boards. To simplify explanation, the relative image brightness produced by a medium or surface at a cer-tain wavelength, whether by refiectance or transmittance, is described as the intensity of light transmitted by the medium or surface at that wavelength.

Although a wide range of wavelengths of low intensity are included in each spectrum 4 and 6, the human eye ydoes not tend to see several colors simultaneously.

Rather it tends to perform an averaging or integrating function for wavelengths within the range in which it is sensi-tive which are present at relatively great intensities and to see a single spectral or non-spectral color defined by the average or integrated function of those wavelengths. The wide range of visible wavelengths present at rela-tively low and level intensities, such as those below about i6800 angstroms in the spectrum 6 of the second ink, have no significant effect on this and are effectively ignored by the eye so far as color perception is concerned. Where there are no relatively great intensities at wavelengths within the visible spectrum to which the eye is sensitive, as in the case of the spectrum 4 of the first ink, the eye tends to perceive an absence of color, i.e., black, and the wide range of visible wavelengths present at relatively low intensities are effectively ignored.

The first ink therefore appears black. The second ink, represented by fine line 6 in FIGURE 2, rises sharply to substantial intensities representing reflectance or transmission of well `over twenty percent of the available light at wavelengths above about 6800 angstroms. Since the eye still has some sensitivity at these wavelengths, there is a slight, discernible dark red hue to the second ink.

However, the relative sensitivity of lthe eye in the region of these peak wavelengths above 6800 angstroms, as illustrated in FIGURE 2, is so slight that at a given level of illuminati-on-particularly in contrast to a background containing the same level of illumination over a substantial range of wavelengths in the region between about 5000 and 6000 angstroms in which the eye is relatively quite sensitive-the dominant impression created by the second ink represented by fine line 6 is black. In other words, the ink is so dark that it appears to have no color at all.

In tests of this invention by applicants, children have been found to enjoy fully the use of the invention with closely similar colors such as the first and second inks represented by lines 4 and 6 in FIGURE 2 even -though painstaking examination of the two colors under strong illumination without the use of any optical filtering means may reveal slight differences between the two colors. Hence, for the present purposes, two colors are considered indistinguishable or inseparable by the naked eye even though close scrutiny under good conditions will reveal some slight differences between them.

Broken line 8 in FIGURE 2 indicates the transmission characteristics of a simple optical filter. The ordinates for the filter indicates the percentage of light transmitted by the :filter at the different wavelengths defined by the corresponding abscissas. Filters having such characteristics are widely used in photography, and may be readily and inexpensively obtained. Generally they are a colored plastic or glass which transmits certain visible wavelengths of light and blocks others.

As indicated schematically in FIGURE 2, such filters can provide a relatively sharp dividing line between Wavelengths which are transmitted and those which are not. There is almost always some loss of light at all wavele-ngths in transmission through a filter, bu-t to the right of the steeply vertical portion of broken line 8 in FIG- `URE 2, beginning at about 6500 angstroms, the filter transmits substantial intensities of the light at the corresponding wavelengths; while to the left of this steeply vertical portion of broken line 8 the filter transmits no substantial or perceptible light at the corresponding wavelengths. The blocking action of the filter does not require that the blocked wavelengths not be transmitted at all; it is substantially as effective so long as there is a marked difference between the transmittance at the peak regions and the transrnittance at the blocked wavelengths. The operation of the -filter may also be effective even though it has other regions of peak transmittance outside the area of the spectrum in which it provides the distinctions and contrasts described herein.

Since all Visible wavelengths above 6500 angstroms produce the sensation of a red or dark red color, the only color which is transmitted by this filter is -a red or dark red. Hence viewed through the filter having the characteristics indicated by broken line 8 in FIGURE 2, the first ink having the characteristics indicated by heavy line 4 in FIGURE 2 continues to appear black and quite distinct against its red or dark red background.

The second ink having the characteristics indicated by fine line 6 in FIGURE 2, however, produces substantial intensities (or relative image brightness) in the presence of light at wavelengths within the range of wavelengths transmitted by -the filter. In fact, by comparing the areas under fine line 6 and broken line 8 of FIGURE 2 in the region between about 6500 angstroms and 7000 angstroms, which is the only effectively visible light transmitted Iby the filter, it appears that about two-thirds as much energy is received from the second medium as from a white surface in a white light when both are viewed through the filter. Only a small fraction of this amount of light energy is received from the first medium, represented lby heavy line 4 in FIGURE 1, when viewed through the filter. Hence there is only a small contrast between the marks in the second medium and their background, but a marked contrast between the marks in the first medium and the background. The marks in the second medium will therefore appear noticeably faint or, depending upon the adaptation of the viewers eye to the decreased level of illumination through the filter yand the intensity of the light source in the dark red wavelengths, they may be invisible. So long as any substantial illumination is perceived through the filter, however, the marks in the first medium will always be distinctly `and contrastingly black.

A child can therefore write a secret message in the first ink or other medium, spacing the letters or symbols apart in whatever manner yhe desires. He can then intersperse among them other letters and symbols written in the second ink or other medium. In a simple line message, for example, "l2 steps may be written .1..2s..t.ep..s. in the first ink, Iand random letters and numbers inserted in the second ink to provide a completed code appearing 5 l 342sadtfepqvsr.

Similarly, graphic messages such as a picture or a map for example, whether serious or amusing, may be encoded by drawing them in the first ink and then adding additional drawing in the second ink which either obscures the graphic message and renders it unintelligible, or changes it so that it is affirmatively deceptive. Decoding can be accomplished immediately by viewing the completed object through the filter.

Many other utilizations of this invention, in which some sort of marking is coded by adding separate markings in an otherwise indistinguishable medium which may be distinguished by an optical filter, so that decoding is accomplished by viewing the completed production through the filter, will occur to those skilled in the art. Coding, as used herein, refers to obscuring or distorting a marking by the addition of further markings; decoding means restoration of the separate visibility of the original marking.

It also will be understood by those skilled in 4the art that the same color often may be produced by the combination of light at two or more wavelengths as is produced by light at a single wavelength representing an averaging or integration of the two combined wavelengths. Similarly, two or more combinations of wavelengths may effectively produce the same color impression; and this is true for both spectral and non-spectral colors. Further, the ability of the human eye to discriminate different wavelengths is not so precise as the ability of optical filters to separate such wavelengths. Particularly where immediate side-by-side comparison is not present, as in verbal messages and most line drawings on a contrasting background, the normal observer finds it difficult or impossible to distinguish between wavelengths less than about 500 angstroms apart. Optical filters, however, can discriminate between blocking or substantially transmitting wavelengths within much narrower ranges. Viewed through a filter whose 'boundary lies between two such closely similar wavelengths, the two wavelengths of light, even though less than 500 angstroms apart, will be readily distinguished by their contrasting intensity, if not by their color.

FIGURE 3 illustrates, in a highly schematic graphic form, the spectra of two green media. Heavy line lrepresents the spectral analysis of the first medium, which is composed of wavelengths around 5250 angstroms in the green region of the spectrum. Practical pencils, inks and other coloring medias very seldom have such clean and simple spectra. However, they do have regions of peak wavelengths (i.e., dominant regions of high refiectance or transmittance) such as that falling under heavy line 10 in FIGURE 3. The relative differences between such regions of principal or major intensity land the fluctuating lower levels of minor intensity such as those below about 6800 angstroms in the spectral analyses 4 and 6 of FIG. URE 2 are more important in determining the color of the medium than the absolute levels of intensity. Changes in absolute level of intensity across the visible spectrum,

6. without changes in relative intensity, tend merely to affect the grayness of the color.

Fine line 12 in FIGURES represents a coloring medium which has two regions of major intensity; one in the blue part of the spectrum around 4500 angstroms, and a second in the yellow area around 6000 angstroms. This second medium is perceived as a green color indistinguishable by the unaided eye from the first medium having a single dominant wavelength around 5250 angstroms. Again, most media would have minor levels of intensity at other wavelengths outside the two regions of major intensity which, as complementary wavelengths, produce the color corresponding to the domin-ant wavelength of the first medium.

Broken line 14 in FIGURE 3 represents the transmission characteristics of an optical filter. Marks made in the two media, when viewed through such a filter, appear as a distinct black and a noticeably fainter blue, against a generally blue background. None of the wavelengths of the first ink are transmitted by the filter, so it appears entirely black. None of the yellow wavelengths of the second medium are transmitted by the filter, but all the wavelengths in the blue region of the spectrum are transmitted. Marks in the second medium therefore appear as a darker blue against a `blue background. However, their intensity is such that there is a less intense contrast with the 'background than is provided by the first ink viewed through the filter, so that they are distinguishable 'both by their color as well as by their contrast in intensity. Hence a message written in the first ink may be encoded by the addition of confusing m-arks in the second ink, and then decoded by use of the filter.

Colors having many other combinations ofv dominant or complementary wavelengths of principal intensity are feasible. So long as two `or more media which have the same apparent color to the naked eye achieve this color by different combinations of wavelengths of peak intensity, separation of the media, either by changes in the `contrast of the -marks or in their color (or both) is possible by the use of optical filters. One medium viewed through the filter will appear distinctly fainter than another, or the apparent color of one or more media will -be changed when viewed through the filter, so that the two no longer appear the same and the messages encoded in them may be distinguished.

However, media in which separation depends upon selective blocking of one or more regions of major intensity at complementary wavelengths or selective blocking between two dominant wavelengths which are so close together (less than about 500 angstroms apart) that their colors are indistinguishable to the naked eye, `are not preferred at present. It appears more economical and efficient to use black or nearly-black colors. All blacks, so far as color is concerned, are the same even though their peak wavelengths beyond the visible spectrum may be quite different. Therefore, in la black system, such as that illustrated in FIGURE 2, one medium requires no careful control or special characteristics so long as it has no major intensities within the visible spectrum. The other medium, of course, must have a peak intensity (which is a region, i.e., band, of wavelengths `centered around a particular wavelength in which relatively great intensities of light are produced by reflectance or transmittance) near the end of the spectrum, but that is all. Similarly, the filter need not be so elaborate as highly selective interference filters operating in the middle region of the visible spectrum, so long as it transmits significant intensities only in the end region of the visible spectrum around the wavelength of the second medium.

Similarly, to achieve economy, the use of more than two indistinguishable media or more than one filter, is not presently preferred.

Since markings in the two media should be substantially indistinguishable to the naked eye, the instruments with which the markings are made, whether they be pens, pencils, brushes or other means for applying the media to a surface, preferably are the same for both media so that the markings cannot Ibe distinguished by breadth, heaviness, texture, or the like. The media Imay be applied by separate instruments; preferably, however, they 'are incorporated in va single unit which lessens the likelihood of loss yof part of the game apparatus and which may add to a childs pleasure in playing the game.

FIGURE 4 is 1a perspective view of such a unit, in the form of a pen which has the appearance of an ordinary writing instrument. 'The construction of this pen is more particularly the subject of our co-pending application entitled, Pl-ay Instrument for Games lof Intrigue, filed herewith.

The pens outward appearance includes its barrel 30 and top 66 with a conventional clip 31 for holding the pen in a users pocket.

However, the features of the pen which render it particularly appropriate yas part of a code game Ias herein described, may be understood with reference to FIGURE 5. The pen -barrel 30 defines an internal cavity 36 with a tip Iopening 38 at yone end and a cylindrical opening 40 rat the other end. The barrel 30 'also includes opposed elongated slots 32 and 34. A divider 42 is centrally and longitudinally positioned within the cavity 36 intermediate the openings 32 and 34, and held at its outer edges (not shown) by the walls of pen ybarrel 30, to divide the cavity 36, in that area, into opposed compartments 44, 44. A first push-button cartridge extender 46 is disposed in one compartment 44 with its button 48 projecting through the adjacent opening 32. A second push-button cartridge extender 50 with push-button 52 is disposed in the other compartment 44 so that push-button 52 extends through the adjacent opening 34 in the pen barrel 30.

Two conventional ball point pen cartridges 54 and S6 with writing tips `55, 57 .at their outer ends are positioned within cavity 36 with their inner-ends respectively in the compartments 44. A spring retainer 58 held by the walls of barrel 30 forwardly of the divider 42 in cavity 36 defines apertures receiving the bodies of the cartridges y54 and 56. The cartridge extenders 46 and 50 include abutments 58 and 60 which engage the inner ends of the cartridges 54 and 56. These abutments 58 and -60 ialso serve as retainers for coil springs A62 and 64. The coil springs 62 land v64 telescopically receive the bodies of the cartridges `54 and '56 within the respective compartments 44. Each extender 46 and 50 includes a ledge 49 adjacent lan integrally formed cantilever flexible spring element 51. When an extender 46 or 50 is moved forward manually, the flexible spring element y51 engages the divider 42 and biases ledge 49 youtwardly into interfering lock with the edge of slot 32 or 34, as is shown with reference to extender 50. The related ink cartridge is biased to extend through tip 38 and the related coil spring cooperates to maintain both the lock and cartridge extension. Pushing the related push-button 46 or 52 inwardly disengages the related ledge 49, Aand the related coil spring 62 or `64 causes the cartridge to return as shown at 46.

The hollow cylindrical pen top 66 telescopically receives the end of pen barrel 30 and includes, in the area of this telescopic reception, an annular internal shoulder 68. Pen ebarrel cap 70 is tixedly disposed within the cavity opening 40 to close and seal cavity vopening 40. Annular outwardly extending ledge 72 engages internal shoulder 68 and prevents disassembly yof the top 66 from the pen barrel 30. Flexible grommet seal 74 is secured, las at 76, to the barrel cap 70 and is in continuous peripheral engagement with the inner surface 78 of the pen top `66. Pen top cap 80 is secured to the external terminus of pen top 66 to cover and seal the end of top 66. Pen top cap 80 includes pin hole opening 82 which communicates between internal cavity 79 and the atmosphere.

Pen top `66 is slidably movable on pen barrel 30, so that the size of cavity 79 may 'be varied by reciprocation of pen top 66. The pen therefore may lbe used as a .water pistol by depressing pen top -66 on pen barrel 30, placing it under Water, extending the pen top 66 relative to pen barrel 30 to fill the cavity 79 with water, and then pointing the pen at a target and depressing the top 66 relative to the barrel 30 to shoot a stream of water lat the target.

Quite aside from childrens notorious fondness for water pistols, the pen when provided with a rst ink such -as that represented by line 4 in FIGURE 2 in one of its cartridges, such as cartridge 54, and with a `second ink such as is represented by line 6 in FIGURE 2 in the `other cartridge 56, is highly attractive to a child simulating the .activities of a spy or counter-spy. The pen provides him with a means to encode lmessages, and the buttons 48 and '52 of push-button cartridge extenders 46 and `50 preferably are formed in different colors lor otherwise differentiated so that the child may know Iwhich ink the message should lbe writen in, and which ink should be used to `add the deceptive encoding marks. The pen also, Ihowever, adds to his make-believe simulation of a spy by appearing to .be an innocuous writing instrument yet incorporating an operative toy weapon such as a make-believe spy might use to shoot poison -at his enemies.

The simulation preferably is carried further by incorporating the optical lter means in some innocuous object such as the lenses of what appears to be ordinary sunglasses; or it may be incorporated as the lens of a simulated detectives magnifying glass.

The pen illustrated in FIGURES 4 and 5 also serves to minimize the possibility that a child may l-ose part of the game apparatus by securing both inks in one unit. This may be carried further by providing a pen, for example the pen shown in the partially lfragmentary FIGURE 6, in which the lter means as well as the two marking media are securely incorporated in the same unit. In FIGURE 6 the semicylindrical pen top 66 is rigidly secured to the pen barrel 30. The semicircular pen top cap 80', which may be formed integrally with the semicylindrical pen top 66', is pivotally joined by hinge 81 to semicylindrical panel 83 which is formed of the plastic or glass optical ilter material. The panel 83 is restrained in closed position immediately adjacent the semicylindrical pen top 66 by exible catch 84 but may be swung out into the opened viewing position illustrated in FIGURE 6 when the child wishes to decode a message. The pen thus secures against accidental loss, in one unit, both the marking media and the optical Iter.

It will be understood that although the filter means preferably are used by putting them immediately adjacent the viewers eye, they may also be used by putting them directly on top of the message to be decoded, or even by interposing them between the light source and the message to be decoded, if other sources of light or the relative image brightness of the surroundings do not prevent adaptation of the viewers eye to the light transmitted from the media.

What is claimed is:

f 1. A code game comprising:

a first marking medium having given optical filter response characteristics;

a second marking medium having given optical lilter response characteristics different from that of said rst marking medium,

said two marking media being substantially indistinguishable from each other to the unaided human eye,

said media being adapted to co-act to effect a composite presentation of information including in said composite presentation a component presentation of information provided by one of said media,

said component presentation being substantially indistinguishable from said composite presentation to the naked eye;

and optical filter means for distinguishing said first and second marking media to make Visible the image formed by said component presentation while substantially concealing the image formed by the remainder of said composite presentation.

2. A code game as defined in claim 1, wherein said first color has minor intensity at a wavelength within the visible spectrum, and

said second color has major intensity at said wavelength.

3. A code game as defined in claim 2, wherein said filter means transmit said wavelength and block other wavelengths within the visible spectrum.

4. A code game as defined in claim 3, wherein said filter means have one region of peak transmittance within the visible spectrum, said region including said wavelength.

5. A code game as defined in claim 4, wherein said first color is black.

6. A code game as defined in claim 5, wherein said second color is a nearly-black dark red.

7. A code game as defined in claim 6, wherein said filter means block most visible wavelengths below 6500 angstroms.

8. A code game as defined in claim 1, wherein said first color includes a single dominant wavelength,

and

said second color includes complementary wavelengths.

9. A code game as defined in claim 8, wherein said filter means block said dominant wavelength and transmit one of said complementary wavelengths.

10. A code game as defined in claim 1, wherein said first color includes a band of wavelengths of major intensity, and

said second color includes a band of wavelengths of major intensity, said band of said second color including wavelengths not included in said band of said first color and within 500 angstroms of said band of said first color; and

said filter means blocks said band of said first color and transmits part of said band of said second color.

11. A method of operating a code game comprising the steps of:

writing a message with a first marking medium having given optical filter response characteristics;

encoding said message by adding deceptive marks to said mesage with a second marking medium having given optical filter response characteristics different from that of said first marking medium,

said two marking media being substantially indistinguishable from each other to the unaided human eye,

said message and said markings co-acting to effect a composite presentation of information including in said composite presentation a component presentation of information provided by said message,

said component presentation being substantially indistinguishable from said composite presentation to the naked eye;

and viewing said composite presentation through optical filter means for distinguishing said first and second marking media to make visible the image formed by said message while substantially concealing the image formed by said second marking medium, whereby said message is decoded.

12. A code game as defined in claim 11, wherein said optical filtering comprises blocking some of the visible wavelengths of light to create a contrast in intensity between said message and said marks.

13. A code game as defined in claim 11, wherein said optical filtering comprises blocking some of the visible wavelengths of light to create a contrast in color between said message and said marks.

14. A code game as defined in claim 1, wherein said first marking medium has major intensity at a second visible wavelength, said second visible wavelength being within 500 angstroms of said first visible wavelength, and

said filter means block said second wavelength.

15. A code game as defined in claim 1, wherein said first marking medium has major intensities in two bandsv 0f visible wavelengths, and

said filter means block one of said bands and transmit the other of said bands.

16. A code game as defined in claim 1, wherein said filter means are formed as spectacle lens, and including a spectacle frame supporting said filter means.

References Cited by the Examiner UNITED STATES PATENTS 14,129 5/1916 Le Fever 222-79 1,422,527 7/ 1922 Berger. 2,529,764 11/1950 Dufilho 120--1 2,676,570 4/1954 Fahringer 1Z0-14.5 2,718,749 9/1955 Florman 120-1 2,865,533 12/1958 Taylor 120-1 3,081,088 3/1963 Kast 35--9 3,174,231 3/1965 Schure 35-9 3,175,303 3/1965 Kirkconnell 35-9 EUGENE R. CAPOZIO, Primary Examiner.

JEROME SCHNALL, Examiner.

S. M. BENDER, Assistant Examiner. 

1. A CODE GAME COMPRISING: A FIRST MARKING MEDIUM HAVING GIVEN OPTICAL FILTER RESPONSE CHARACTERISTICS; A SECOND MARKING MEDIUM HAVING GIVEN OPTICAL FILTER RESPONSE CHARACTERISTICS DIFFERENT FROM THAT OF SAID FIRST MARKING MEDIUM, SAID TWO MARKING MEDIA BEING SUBSTANTIALLY INDISTINGUISHABLE FROM EACH OTHER TO THE UNAIDED HUMAN EYE, SAID MEDIA BEING ADAPTED TO CO-ACT TO EFFECT A COMPOSITE PRESENTATION OF INFORMATION INCLUDING IN SAID COMPOSITE PRESENTATION A COMPONENT PRESENTATION OF INFORMATION PROVIDED BY ONE OF SAID MEDIA, SAID COMPONENT PRESENTATION BEING SUBSTANTIALLY INDISTINGUISHABLE FROM SAID COMPOSITE PRESENTATION TO THE NAKED EYE; AND OPTICAL FILTER MEANS FOR DISTINGUISHING SAID FIRST AND SECOND MARKING MEDIA TO MAKE VISIBLE THE IMAGE FORMED BY SAID COMPONENT PRESENTATION WHILE SUBSTANTIALLY CONCEALING THE IMAGE FORMED BY THE REMAINDER OF SAID COMPOSITE PRESENTATION. 